Electrostatic shields



June 2, 1959 o. T. MclLvAlNE 2,889,484

ELEcTRosTATIC sHIELDs Filedspc. e, 1955 annua aruanavdumrunll'114141111105101 ravauuxvnln I N VENTOR ATTORNEY Untd States Patent s2,889,484 ELECTROSTATIC SHIELDS 'Oran T. Mcllvaine, St. Charles, Ill.Application September 6, 1,955, Serial No. 532,687 3 Claims. (Cl,31734-3713) This application is a continuation-impart of my priorapplication led February 25, 1952, Serial No. 273,181, now abandoned.

This invention relates to improvements in electrostatic shields adaptedfor use with` electron or space. discharge tubes, gas lamps, televisiontubes, etc., to create a fixed r permanent shield or grid bias withoutthe use of voltage or current.

This is an improvement on the electrostatic shields set forth in myprior Patent No. 2,040,753, granted May l2, 1936,V which described anelectrostatic shield for a gas discharge lamp that has been widely usedsuccessfully for many years, especially in the Neon sign industry.However, the shielding eifect was obtained such gas discharge lamps byvirtue of the electrons produced from the arc discharge within the lamp.

One object ofV this invention is to accomplish ,an -electrostaticshielding elfect Without the use of voltagev of any kind.

Another object of the invention is to permanently charge anelectrostatic'shield made of dielectric material which may be used inconjunction with electrodes and many other uses for obtaining eiectiveshielding thereby without the use of voltage or current.

Still another object. of the invention is to .provide for a permanentelectrostatic shielding effect for many uses, including. electron tubes,by permanently charging a suitable plastic or other fusable dielectricVmaterial which may be placed in proper relation to. the, article to beshielded and thereby produce. an effective permanent shielding action.

I have discovered that a permanently charged electrostatic shield may bemade from a suitable dielectric material which is melted and placed in astrong electrostatic eld'. If this material is allowed to cool andsolidify in the field, the materialr will. have a permanent charge.

which may be either positive. or negative according to the iieldin'whichit was placed. Ifa section of this material is placed near the articleto be shielded, itwill have a guiding effect and desirable propertiessuch as those which were obtained by the electrostatic shields describedin my Patent No. 2,040,753.

Several embodiments of this invention are illustrated in, theaccompanying drawings in which:

Fig. l is a longitudinal section through a portion of a space dischargetube show-ing the invention applied thereto;

Fig. 2` is aside elevation of tronic tube; and

Fig. 3 is a longitudinal. section, partly inside; elevation, of an oilburner assembly showingthe invention applied thereto.

The permanently charged dielectric materialsnitable for this purpose maybe any of the usual plastics, such as synthetic resins, vinyl resin,acrylic resin, acetate or polystyrene, or of glass. Such non-conductorsof electric current are capable of being melted and then solidified ashielded grid for an elecorcooled in an electrostatic field. It may bepossible to use a ceramic or other such material which will melt at ahigh temperature, especially for use in high temperature work.

The material of the character described above should be softened eitherto a plastic state or melted to liquid form, and when the moleculesthereof are uid, it is placed in an electrostatic eld, transversely ofthe field, for example, and remains in such field until it has set orhardened into solid form. When so treated, the material will have apermanent electrostatic charge. It can be charged either positive ornegative according to the. character of the electrostatic field and thedirection of the material with respect thereto. The extent of .thecharge may be varied, as desired, according to the use of theelectrostatic shield.

One use of such material is illustrated in Fig. l in which an elongatedtube having a wall of electromagnetic. Wave transmissive material,generally designated at l, forms a part of a space discharge tube iilledwith a suit able gas, such as Neon, or one of the other inert gasesaccording to the use of the tube. An electrode is indicated at 2,mounted in the tube l, and supported by a lead Wire S. The electrode 2is shown as hollow in this example of the invention.

The electrostatic shield is indicated at 4 and is mounted in the tube lin any suitable manner surrounding thek electrode 2. This electrostaticshield 4 is of the character described above, whereby it is permanentlycharged without requiring any current or voltage for its effectiveriess.V

Where. the electrodes are used in space discharge lamps, an intensepositive-column discharge always tends to produce what is known assputtering of the electrodes, with consequent blackening of thecontainer walls. The electrostatic shield surroundingtheelectrode 2prevents such sputtering on the walls and confines the discharge to theinterior of the hollow electrodes, there'- by preventing, or at leastretarding the blackening of the container. The permanently chargeddielectric materia-l of the character described above produces theeffect set forth in my prior Patent No. 2,040,753, Without the use ofvoltage or current as was requiredV therein.

It has been found that fluorescent lamps often blacken at the ends,resulting in a failure of operation. I have discovered that theincorporation of such electrostatic shields as described herein, aroundthe electrodes of the lamps at the ends thereof, prevents the blackeningand prolongs the life of the lamp many times. The shield v may be usedalso in high temperature lamps for the purillustrated in Fig. l, ashieldv with a positive charge, the

arc can be started easily. If, as in the case of Neon signs,`

a negative shield is needed to prevent the electrode from sputtering, apositive shield of a few volts is used to start the arc instead of theusual high voltage as heretofore required, and as soon as the arc isstarted, the shield' operates as in my former patent, thereby servingboth purposes.

I also applied this permanently electrostatic shield to a grid of anelectron tube, as indicated at 11 in Fig. 2, to give a permanent chargeor bias, and thereby eliminating the C battery or grid voltage. The gridcan be operated l in this manner either negative or positive, as thecase may be. The grid Il is constructed in the usual manner either froma wire coil or of perforated plates, or otherwise, and is thon coatedwith glass, plastic, or other suitable dielectric material, as describedabove, by dipping in the softened or melted material, which is thencharged, as also described above, and the grid will have a permanentcharge or bias. This bias can be changed by the input voltage, as in theusual manner of obtaining ampliiication.

The grid is prepared, as described above, and used in the conventionalmanner of employing grids in electronic discharge tubes except that thegrid having the electrostatic shield coated thereon makes unnecessarythe conventional C battery. The amount of charge placed on the grid willbe determined by the field in which it is placed. For instance, if it bedesired to provide a 3-volt negative bias on the tube, this may beprovided by a 3-volt charge on the shield material. In like manner, thematerial can be charged with volts, or other voltage desired, eitherpositively or negatively. Thyratrons often require as much as Volts tostart the tube, but if constructed with a positively charged grid, sucha tube may be started on its operating voltage. This grid, so made, maybe used in any place where a battery-charged grid has been usedheretofore.

In television, or cathode ray tubes, these electrostatic plates can beused to replace the usual focus coils or permanent magnets, or theconventional electrostatic plates, thereby saving power for the focuscoil and making a much lighter assembly, as well as saving appreciablyin the amount of wire used, which reduces the cost of the tube.

The degree of bias on the control element is determined by the voltageused in the electrostatic eld when making the shield element. Forexample, if a grid with a 10 volt bias were desired, a iield of perhapsl0() volts would be used. If a 20 volt bias were desired, a field of 200Volts would be used. This may be varied according to the material usedand the time in the field, but could be determined readily.

In thyratron tubes, a common source of trouble is the requirement forhigh starting voltage, in many cases requiring several hundred volts tostart the operation of the tube, whereas after it has been started, thearc drop is only a few volts, approximately 5 or l0. This is caused bythe negative grid effect of the various elements. By using a positivegrid prepared with the permanently charged dielectric material, asdescribed above, this trouble would be eliminated. As soon as the tubestarts operating, the circuit would supply the proper grid voltage forcontrol.

I have also found these electrostatic shields of this character usefulin other iields, as in the oil burner illustrated in Fig. 3. The burnerelement is shown at 2l. The burner element 2l has a nozzle at thedischarge end thereof, adapted to spray oil in an outward directionwithin the combustion chamber within which combustion may take place. Inthis embodiment as illustrated, the burner element 21 is mounted withina draft tube 22 spaced therefrom for the circulation of air within thedraft tube to support combustion.

When the oil is sprayed from the nozzle of the burner element at usualoil burner presusre, or, for instance, at 100 psi., it impinges againstthe walls of the combustion chamber and is attracted thereto, thuscausing carbonizing of the combustion chamber.

I have provided a permanently charged electrostatic shield 23 mounted onthe inner wall of the combustion chamber, or portion of the draft tube22, where the vapor or spray from the nozzle of the burner element 21otherwise would strike the combustion chamber or burner tube. A negativecharge onthe shield 23 would cause the droplets of oil to be repelledfrom the walls of the combustion chamber or burner tube, thus preventingtheir accumulation thereon and thereby preventing the carbonizing ofthis portion of the oil burner structure. In most instances the vapor orspray of oil would be charged negatively by the force of oil passingthrough the nozzle 21, in which event a like charge on ltheelectrostatic shield 23 would cause these particles to be repelled.However, if in any installation the particles should be chargedpositively, the positive charge may be applied to the shield 23.

The repelling of the droplets of oil from the walls of the combustionchamber or of the air tube 22 will cause these to be mixed with the airsupplied and thus carried along in the air tube for combustion therein,or in the combustion chamber, without an accumulation of carbon on theadjacent portion of the burner.

These electrostatic shields may be uesd in many other fields, such asair or smoke filters. For instance, a ring of the material may be placedin the tip of a cigarette and will act to trap the tar substance in thesmoke and hold it on the ring. A sheet of this material placed in theair passage, or in a vacuum cleaner, will remove the dust from the airwithout the use of high voltage, nor the expensive, complicated, andhazardous equipment that would be required otherwise.

While I have illustrated and described certain embodiments of theinveniton, it is recognized that other variations and changes may bemade therein Without departing from the invention, as set forth in theclaims.

I claim:

1. An electronic discharge lamp comprising an envelope having a wall ofelectromagnetic wave transmissive material, an electrode mounted Withinsaid envelope, and an electrostatic shield substantially surroundingsaid electrode and positioned between said electrode and said wall insuch fashion as to shield said wall from electrode sputtering, saidelectrostatic shield comprising a dielectric material having a permanentelectrostatic charge.

2. An electric lamp comprising a closed envelope having a wall ofelectromagnetic wave transmissive material, an inert gas within saidenvelope, an electrode mounted within said envelope, and a tubularmember of permanently charged dielectric material surrounding saidelectrode, said tubular member being positioned between said electrodeand said wall so as to prevent blackening of said wall.

3. In an oil burner, the combination comprising an elongated nozzle forspraying oil, a draft tube concentrically mounted around and spaced fromsaid nozzle, and an elongated tubular member of permanently chargeddielectric material mounted in front of said nozzle and between saidnozzle and said draft tube to electrostatically repel the oil sprayformed when said nozzle is spraying oil, thereby preventing theaccumulation of carbon deposits.

D. Van Nostrand Co., International Dictionary of Physics andElectronics, page 275, Princeton, NJ., 1956.

